This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
HON. MARSHALL P. WILDER, President American Pomological Society: - Dear Sir - The Committee appointed at the last annual meeting of this Society, to investigate the cause of pear blight, and, if possible, recommend a remedy or preventive therefor, beg leave to submit as follows:
The task allotted to your committee is connected with unusual difficulties, as the subject is one that has for more than a quarter of a century remained an unsolved problem. We therefore entered upon the performance of our duties with the conviction that our efforts must fall short of doing justice to the object in view.
Pear blight assumes different forms and has consequently different causes for its origin. One form attacks trees gradually; its approach is slow and may be detected for months, and often daring the preceding season of growth, before the tree is fully affected, This form, which may be termed gradual blight, is seen at all seasons during the period of active vegetation, from early spring until September. Its progress is usually arrested by a liberal top-dressing of liquid manure, so far as the roots extend and a severe cutting back of the branches. This must be done whenever the tree assumes an unhealthy appearance. The cause, then, may be safely attributed to exhaustion, and the remedy consists in replenishing the exhausted supply of plant food. This form of blight is often noticed in orchards left unworked and where the annual or biennial top dressing with fertilising agents has been withheld.
Another, and this is the most fatal form, attacks a tree or a portion of it suddenly, causing the affected part to blacken in a few hours after the tree is struck; this is commonly termed Fire blight. This form is periodical in its attacks and migratory, as it seldom remains permanent in a locality, but leaves an interval of from ten to fifteen years between its occurrenco. Its greatest intensity is on its first appearance, which occurs usually when the fruit has attained half its size; it decreases as the season of vegetation advances, but reappears again the following summer with less of its previous intensity. After decimating a section of country during two consecutive seasons, there will be ad interval of a series of years, during which, blight in its other forms may occur, but there will not be a wholesale destruction as during the prevalence of epidemic blight. Every observation tends to the conclusion that fire blight is caused by symotic fungus, whose presence is not detected until life is destroyed in the affected parts. This form offers a wide field for the investigation of microscopists, and from their future labors, we hope to arrive one day at the origin of this fungoid growth.
We are unable to arrive at a satisfactory conclusion, as to what peculiarities of soil and temperature induce the favorable conditions for the development of this fungoid vegetation.
In the Experimental gardens of the Department of Agriculture at Washington, the following mixture is prepared: Place a half-bushel of lime and six pounds of sulphur in a close vessel, pour over it about six gallons of boiling water, adding enough cold water to keep it in a semi-fluid state until cold. It is used as a wash and applied to the trees and branches as high as can be reached. It should be applied two or three times during the summer. Since this preparation was used, no trees thus treated have been lost, although small limbs not coated with the mixture were attacked and destroyed. Carbolic acid has also been used without any perceptible difference in the result from the lime and sulphur mixture. Boiled linseed oil, applied to the trunk and limbs has been tried near Norfolk, Va., with marvelous cures, as reported. We mention this instance of the use of an extraordinary ingredient resulting in good effects, as contrary to what is usually the result when using this application upon the body of trees, its effects being to seriously injure the tree if it does not destroy it.
Still another form of blight is doubtless caused by mechanical action, by the rupture of tissues consequent to a sudden superabundant flow of sap. This attacks only our most thrifty growing trees, either in early spring, when vegetation first becomes active, or after a period of drought and partial stagnation of vegetation, when abundant rains suddenly force out a luxuriant growth; moderately vigorous trees are never attacked. It is often noticed in very vigorous trees that the bark of the trunk is split longitudinally; whenever this is apparent, such trees are always free from this form of blight, as the pressure upon the cellular and vascular tissues has been relieved. From a series of experiments commenced in 1857, it is demonstrated, that whenever trees whose bark had been longitudinally incised and divided, never showed any signs of this form of blight.
Peculiar methods of culture undoubtedly influence the causes of blight; but upon this there exists a wide range of opinion. Clean culture and repeated stirring of the soil, while it may in many instances be conducive to most beneficial results, will often cause a total destruction of a pear orchard. In seasons of zymotic fungoid or fire blight, highly cultivated trees fall early victims to the scourge, while those cultivated in grass with an annual top dressing of manure usually escape the contagion.
The third form of blight caused by mechanical action is seldom found in orchards where the soil is left undisturbed, but is so common in gardens or where the trees are thoroughly worked, that it has become only a question of time for the entire destruction of one's orchard.
In the Southern States this form of blight is the most destructive, as it has become endemic to all highly cultivated soils. Wherever the land is allowed to become coated with grass or weeds, but kept cut down every few weeks and an annual top dressing of manure is applied, the result has been most satisfactory in an abundant crop of fruit and an almost entire freedom from blight.
P. J. BERCKMANS, JOSIAH HOOPES,